Enhanced Electrocatalytic Reduction of Oxygen at Electrodes Coated with a Multi-Metallic Co(II)/Pt(II) Porphyrin
- 1 Department of Chemistry, University of Dayton, Dayton, USA
- 2 Department of Chemistry, University of Dayton, Dayton, USA
Abstract
Edge plane pyrolytic graphite (EPG) electrodes coated with the Co(II)/Pt(II) 2 analog of 5,15-bis-(4-pyridyl)-10,20-bis-(3-methoxy-4-hydroxyphenyl)porphyrin undergo an electrochemical-chemical-electrochemical (ECE) reaction when anodically scanned in 1.0 M sulfuric acid. The new redox couple formed from this anodic conditioning of the coated electrode is dependent on the pH of the solution. Roughened EPG electrodes coated with the Co(II)/Pt(II) 2 trimetallic porphyrin show a catalytic shift of 400 mV for the reduction of O 2 when compared to the reduction of O 2 at a bare EPG electrode. An additional catalytic shift of ca. 150 mV is observed for O 2 reduction at an EPG electrode coated with the Co(II)/Pt(II) 2 porphyrin which has been oxidized in 1.0 M sulfuric acid. In addition to the added electrocatalysis, a significant percentage of O 2 reduced at the oxidized Co(II)/Pt(II) 2 EPG electrode is converted to H 2 O as determined by rotating disk electrode measurements.
- G. Farmer and D. J. Hamblin, “First on the Moon,” Little, Brown, and Co., 1970.
- S. Wasmus and A. Küver, “Methanol Oxidation and Direct Methanol Fuel Cells: A Selective Review,” Journal of Electroanalytical Chemistry, Vol. 461, No. 1-2, 1999, pp. 14-31.
- H. Jahnke, M. Schonborn and G. Zimmermann, “Organic Dyestuffs as Catalysts for Fuel Cells,” Topics in Current Chemistry, Vol. 61, 1976, pp. 133-181. http://dx.doi.org/10.1007/BFb0046059
- Y. Kiros, “Metal Porphyrins for Oxygen Reduction in PEMFC,” International Journal of Electrochemical Science, Vol. 2, 2007, pp. 285-300.
- J. E. Newton and M. B. Hall, “Generalized Molecular Orbital Calculations on Transition-Metal Dioxygen Complexes: Models for Iron and Cobalt Porphyrins,” Inorganic Chemistry, Vol. 23, No. 26, 1984, pp. 4627-4632. http://dx.doi.org/10.1021/ic00194a043
- C. Shi, B. Steiger, M. Yuasa and F. C. Anson, “Electroreduction of O2 to H2O at Unusually Positive Potentials Catalyzed by the Simplest of the Cobalt Porphyrins,” Inorganic Chemistry, Vol. 36, No. 20, 1997, pp. 4294-4295. http://dx.doi.org/10.1021/ic970516s
- E. Song, C. Shi and F. C. Anson, “Comparison of the Behavior of Several Cobalt Porphyrins as Electrocatalysts for the Reduction of O2 at Graphite Electrodes,” Langmuir, Vol. 14, No. 15, 1998, pp. 4315-4321. http://dx.doi.org/10.1021/la980084d
- C. Shi and F. C. Anson, “Multiple Intramolecular Electron Transfer in the Catalysis of the Reduction of Dioxygen by Cobalt meso-Tetrakis(4-pyridyl)porphyrin to Which Four Ru(NH3)5 Groups are Coordinated,” Journal of the American Chemical Society, Vol. 113, No. 25, 1991, pp. 9564-9570. http://dx.doi.org/10.1021/ja00025a022
- C. Shi and F. C. Anson, “Electrocatalysis of the Reduction of O2 to H2O by Tetraruthenated Cobalt mesoTetrakis(4-pyridyl)porphyrin Adsorbed on Graphite Electrodes,” Inorganic Chemistry, Vol. 31, No. 24, 1992, pp. 5078-5083. http://dx.doi.org/10.1021/ic00050a029
- B. Steiger, C. Shi and F. C. Anson, “Electrocatalysis of the Reduction of Dioxygen by Adsorbed Cobalt 5,10,15, 20-Tetraarylporphyrins to Which One, Two, or Three Ru (NH3)52+ Centers are Coordinated,” Inorganic Chemistry, Vol. 32, No. 10, 1993, pp. 2107-2113. http://dx.doi.org/10.1021/ic00062a038
- C. Shi and F. C. Anson, “Comparison of the Catalytic Reduction of Dioxygen by [5,10,15, 20-tetrakis((pentaamineruthenium(II))4-pyridyl)porphyrinato]cobalt(II) in Solution and on Graphite Electrode Surfaces,” Inorganic Chemistry, Vol. 34, No. 18, 1995, pp. 4554-4561. http://dx.doi.org/10.1021/ic00122a010